(1) Field of the Invention
The invention generally relates to gas permeating or gas emitting systems. More particularly, the invention relates to a gas permeating system using an amorphous fluorpolymer material.
(2) Description of the Related Art
Other permeation devices or tube devices are known in the related art and are widely used to deliver or generate known gas mixtures of various chemicals. Devices in the related art are used for the testing and calibration of air pollution instruments, chemical and petrochemical process analyzers and safety equipment.
An early device was disclosed by Andrew E. O'Keefe in his U.S. Pat. No. 3,412,935 (the '935 patent). In the '935 patent O'Keefe describes the use of material such as sulfur dioxide kept inside a tube made with polytetrafluoroethylene (PTFE), in the form of liquefied gas under its own pressure. The sulfur dioxide will permeate in the form of gas through the solid wall of the PTFE tubing, and the rate remained fairly constant, as long as the tube was kept at a contestant temperature. The permeation rate was however, low generating concentrations in low ppm (parts per million) range; and the permeation rate was substantially dependent on the temperature of the device, in the range of 10 to 15% increase for every one (1) degree Celsius increase in temperature. Similar results have been obtained with other materials such as fluorinated ethylene-propylene (FEP), perfluoroalkoxy fluorocarbon (PFA) and others.
Subsequently, Chand in U.S. Pat. Nos. 3,856,204 and 4,399,942 described the use of silicone material to obtain higher permeation rates and low temperature dependency. However, the use of silicone has been limited to mostly non-corrosive materials and was found unsuitable for gases like nitrogen dioxide and sulfur dioxide.
Paul R. Resnick, Min-Hong Hung and others have developed various types of amorphous fluoropholymer material, more formally known as fluorinated (ethylenic-cyclo oxyaliphatic substituted ethylenic) copolymer, with certain variations commonly known as Teflon AF as a trade name sometimes associated with I.E. Du Pont de Nemours and Company.
In U.S. Pat. No. 5,310,838 issued on May 10, 1994 Hung and Resnick disclosed a Fluoropolymer comprising repeat units of perfluoro-2,2-dimethly-1,3-dioxole with a repeat unit of another fluoromonomer such as tetrafluoroethylene.
In U.S. Pat. No. 5,324,889 issued on Jun. 28, 1994 Resnick disclosed various amorphous perfluoropolymers directed toward the use of cladding materials for optical fibers, encapsulating materials for electronic components, laminates other uses were impervious surfaces were needed.
As the use of silicone in permeation devices has limitations regarding the use of corrosive material there is room in the art for new means and methods of creating gas permeation devices. While the known prior art uses various types of amorphous fluoropholymer materials for impervious surfaces there is room in the art for unobvious or more artful uses for amorphous fluoropholymer materials.